Author round-table 020

Today our theme is Ripple Effect. It's a comparatively new puzzle. There hasn't been a lot of talk about Ripple Effect. What kind of a story can we expect to hear here? The guests are Turing-Joe Jr. and T. Karino. From Nikoli we have Nob and NyanBaz.

NyanBazToday we will talk about only Ripple Effect.

Turing-Joe Jr.OK, here we go.

T. KarinoTuring-Joe Jr. is good at making Ripple Effect. I'm weak at Ripple Effect. And we are the two guests. (laughs)

NyanBazYou got something wrong there. You make a lot of good problems, so we invited you. The other day Turing-Joe Jr. told of his deep contemplation of Ripple Effect in an interview. How about you, T. Karino? Is it just one puzzle among many puzzles?

T. KarinoYes. Ripple Effect is just one of many kinds of puzzles that I make. And then, I'm not good at making it.

NyanBazReally!? But, you have more Ripple Effect problems published than other authors.

T. KarinoIt could just be that other authors are even less good at it than I am or that other authors don't make so many.

NobMaybe so.

T. KarinoI would really like Turing-Joe Jr. to teach me how to make Ripple Effect. (laughs)

NyanBazYou may be on to something, Ripple Effect may be a puzzle where it is hard to create problems for any author.

Turing-Joe Jr.It is easy to go wrong with Ripple Effect. When I began to make it, I failed innumerable times. At a very early stage I decided to make it and always check the problems on the computer.

NyanBazDid you write the program for that by yourself?

Turing-Joe Jr.Yes. I decided to make Ripple Effect on the PC. I wrote a program where I can't input a number if it violates the rules.

NobDo you check problems with your own program, too, T. Karino?

T. KarinoSure.

Turing-Joe Jr.If you try to make Ripple Effect puzzles without using a PC. You will be tripping yourself up. (laughs)

T. KarinoWhen you violate rules and don't notice them, you will make yourself miserable.

NobWhen I notice something having failed, it's difficult to get back on track later. It's difficult to change the shape of a room or cut it into smaller bits.

T. KarinoI sometimes cut rooms into pieces. If I make a Ripple Effect and try not to mess it up, the numbers tend to become large. So I revise later by cutting up rooms.

NyanBazDo you cut up rooms after they are set, too Turing-Joe Jr. ?

Turing-Joe Jr.It happens. But I decide on the biggest number for every problem I do. If it seems to go over that number, I backtrack a little, and redo it.

T. KarinoI basically agree with that. I always want to assume a maximum of 5 or 6. But it doesn't go well on its own.

NobWhen Ripple Effect first appeared in Puzzle Communication Nikoli, there were few contributions of easy problems. I had to make an easy problem because I was the chief editor in those days and I remember that I had a hard time getting it right. It's very difficult to make easy problems with Ripple Effect. I could understand why there were few contributions of easy problems. (laughs)

NyanBazIt becomes difficult when it uses big numbers.

T. KarinoOne thing I learned, it doesn't fail when I put in the same numbers diagonally. With that in, I can fill the board with the rest of the numbers and then later divide into rooms.

Turing-Joe Jr.There is that. I sometimes do it that way, too. But it isn't really good when numbers line up too regularly.

T. KarinoRight, that wouldn't make an interesting problem.

NyanBazWell, authors find it difficult to make them, but they are popular among solvers. In nikoli.com, there are more people solving Ripple Effect than similar Sudoku.

Turing-Joe Jr.But why this popularity?

NobThere are fewer problems that need hard solving methods like Sudoku. Ripple Effect will be solved correctly if you make a steady effort.

T. KarinoI don't think that is it. Looking at it from the solvers, most of the solving methods of Ripple Effect are the same as for Sudoku. So the way of thinking you use with Sudoku works with almost all Ripple Effect problems. That's if you forget about where you have to look with columns and rows.

NyanBazBut there has to be something where Ripple Effect is different from Sudoku.

T. KarinoCouldn't it be because there are fewer numbers to use than with Sudoku? There are few problems that go to 8 or 9 in Ripple Effect. You don't have to look so far. I think that is the reason why it is more interesting than Sudoku.

NyanBazGood point, when you think about 1, you only have to watch the next cell. It's different with Sudoku. You have to look out for 1s in Sudoku all over the place. Because you know you just have to look at the near neighborhood, is that why it is liked?

T. KarinoCompare with Sudoku. I use the same solving methods, just like Sudoku. Especially, I use "reservation" a lot.

NobWhen you make the problems, you can use reservation a lot too. For example, 2 and 3 both must be in one of at most two cells, because there will be no other numbers in those two cells.

T. KarinoExactly that. Methods we use with Sudoku can be used just the way they are.

NobWhen a difficult method like "reservation" is necessary with Ripple Effect, it suddenly becomes hard.

NyanBazYour problems don't call for many difficult methods Turing-Joe Jr. Are you careful not to use difficult methods a lot?

Turing-Joe Jr.I pay a lot of attention to that. Basically I arrange it so you need to look at only one room. I try not to use a method where you pay attention to a specific cell to solve the puzzle.

NyanBazAh, that is how you do it.

Turing-Joe Jr.Even if I do use that method, it would only be at the end of the problem.

T. KarinoIf you do it like that it all becomes so much easier.

Turing-Joe Jr.I don't want to use that. Because I don't think it's so simple really. But it will be easier to catch on to than with Sudoku.

NyanBazIt's interesting that you guys think differently about it.

Turing-Joe Jr.Looking at it another way, one wonderful thing about Ripple Effect is that the difficult Sudoku rule about looking at two columns where two numbers are missing, then finding two rows with the same two numbers missing (X-wing method), in Ripple Effect that can be flagged in easy-to-notice ways. This rule can be highlighted and shown with a careful fitting together of small rooms.

NobYou are able to steer towards something special to look for with the shape of the rooms. With Ripple Effect, you aim for that, and you can actually realize it. Amazing ability!

NyanBazIt may fail at other places, and then it may become possible to solve from another place by some different method. It's difficult to get it completely right.

T. KarinoThat wouldn't be possible for me, yet.

Turing-Joe Jr.I settle on the form of the rooms and that way I can emphasize the place that I want to let solvers pay attention to. I think that is a good point with Ripple Effect. It's the homogeneity, the evenness of the rooms, it's rows, and columns with Sudoku.

NobAnyone can put a 1 into a one cell room.

Turing-Joe Jr.That's a very important point.

NyanBazAre there any thoughts about the numbers that are shown from the beginning? Do you want to reduce the number of those if possible?

T. KarinoIf I have to choose, I want to have fewer of them. But when I make an easy problem, I don't particularly try to keep it to the fewest.

NobHow about you Turing-Joe Jr.? You go out of your way to make the placement of the numbers symmetrical.

Turing-Joe Jr.I try. There aren't many ways to attract attention and make it appealing with Ripple Effect. For that reason I regard the appearance as important.

T. KarinoIt's easy to make a symmetric placement. After that is in place, placing the rest of the numbers becomes symmetric.

Turing-Joe Jr.True enough, but I don't want to put numbers that are clearly unnecessary. Whenever possible I want the solvers to put the 1 into a 1 cell room.

NobYou are thinking about even that!

Turing-Joe Jr.I don't want to pay too much attention to reduce starter numbers. The puzzle can become hard, unexpectedly when a number is removed. When I get stuck with the solution checking, I can increase the number.

NobSAKAMOTO, Nobuyuki makes problems that have a lot of numbers. How do you think about that type of problems? Is it OK or what?

T. KarinoNot completely uncool I think. I admire his problems that have many numbers, but they are well thought out and really good easy problems. I think that way because I'm poor at making easy problems.

Turing-Joe Jr.I think that it's natural to want to reduce numbers when you are used to making problems. However, the result may turn out bad when I reduce (remove) the numbers. Recently I've started to think that authors shouldn't mind it if there is a surplus of numbers.

NyanBazLet's think ahead. Is there a future for Ripple Effect?

Turing-Joe Jr.Do I have to say it? Of course there is!

NyanBazWhat kind of direction is it going in? I wonder it will become a puzzle for just some enthusiasts when we pursue hard ways of dealing with it.

Turing-Joe Jr.I think that one direction is to make the hard ways of doing it look plain and simple.

NyanBazThat's for sure. There would still be room for ideas about how it looks.

T. KarinoI said a little while ago that the basic thought behind solving Ripple Effect is the same as with Sudoku. But I think that new problems become possible using the shape of the rooms.

NobHow about large rooms? The current mainstream in Ripple Effect thinking is for a problem to advance little by little from small rooms with small numbers. You can reverse it when you use big rooms well. The development becomes dynamic when big numbers influence remote rooms like you are making potshots.

T. KarinoNumbers that are needed to be shown will increase when I use big rooms. If that can be settled, I think that it'd be interesting.

Turing-Joe Jr.It seems to be difficult to control where the shots go so solvers enjoy it. However, I am interested in it as an idea, a story to explore. It seems to be potentially pleasant.

NyanBazWell. Ripple Effect is still growing up. Last here today, anything that you guys want to tell solvers?

T. KarinoAt first I want you to feel a fun that is unlike Sudoku in the easy problems.

Turing-Joe Jr.I think that Ripple Effect is a developing puzzle. If you solve many problems from now on, you may get a sense of the development of Ripple Effect.

NyanBazThank you for today! Let's enjoy Ripple Effect, all of us together.